/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using Spring.Expressions;
using Spring.Objects.Factory;
using System.Runtime.Serialization;

namespace Spring.Context.Support;

/// <summary>
/// Represents a reference to a Spring-managed object.
/// </summary>
/// <author>Aleksandar Seovic</author>
[Serializable]
public class ReferenceNode : BaseNode
{
    /// <summary>
    /// Create a new instance
    /// </summary>
    public ReferenceNode() { }

    /// <summary>
    /// Create a new instance from SerializationInfo
    /// </summary>
    protected ReferenceNode(SerializationInfo info, StreamingContext context)
        : base(info, context)
    {
    }

    /// <inheritdoc />
    /// <summary>
    /// Returns a value for the integer literal node.
    /// </summary>
    /// <param name="context">Context to evaluate expressions against.</param>
    /// <param name="evalContext">Current expression evaluation context.</param>
    /// <returns>Node's value.</returns>
    protected override object Get(object context, EvaluationContext evalContext)
    {
        var objectName = ResolveNames(out var contextName);

        var sourceContext = SelectSourceContext(evalContext, contextName);

        return sourceContext.GetObject(objectName);
    }

    private string ResolveNames(out string contextName)
    {
        var hasContextDefined = getNumberOfChildren() == 2;

        if (hasContextDefined)
        {
            contextName = getFirstChild().getText();
            return getFirstChild().getNextSibling().getText();
        }

        contextName = null;
        return getFirstChild().getText();
    }

    private static IObjectFactory SelectSourceContext(EvaluationContext evalContext, string contextName)
    {
        if (contextName != null)
            return ContextRegistry.GetContext(contextName) ?? throw new ArgumentException($"Context '{contextName}' is not registered.");

        if (TryGetFromCurrentContext(evalContext, out var currentObjectFactory))
            return (IObjectFactory) currentObjectFactory;

        return ContextRegistry.GetContext() ?? throw new ArgumentException("No context registered.");
    }

    private static bool TryGetFromCurrentContext(EvaluationContext evalContext, out object currentObjectFactory)
    {
        currentObjectFactory = null;

        if (evalContext.Variables is null)
            return false;

        return evalContext.Variables.TryGetValue(Expression.ReservedVariableNames.CurrentObjectFactory, out currentObjectFactory);
    }
}
